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Abstract:

Disclosed is a method including communicating, by a mobile device, with a
base station via first and second component carriers having different
frequency bands and time division duplexing (TDD) configurations. The
method may include receiving one or more downlink transmissions via the
second component carrier. The method may include selecting a hybrid
automatic repeat request (HARQ) timing sequence based on the TDD
configurations of the first and second component carriers. The method may
include transmitting one or more positive acknowledgment and/or negative
acknowledgement (ACK/NACK) signals, associated with the one or more
downlink transmissions, according to the selected HARQ timing sequence.
Other embodiments may be described and claimed.

Claims:

1-24. (canceled)

25. One or more computer-readable media having instructions that, when
executed, cause a mobile device to: establish a primary serving cell
(PCell) and a secondary serving (SCell) with a base station, the PCell
being established with a first time-division duplexing (TDD)
configuration, the SCell being established with a second TDD
configuration; receive downlink data through the SCell; select a
reference TDD configuration based on the first and second TDD
configurations; and transmit acknowledgement information associated with
the downlink data according to a hybrid automatic repeat request (HARQ)
timing of the reference TDD configuration.

26. The one or more computer-readable media of claim 25, wherein the
reference TDD configuration is different from the TDD configuration
indicated by a system information block of the SCell.

27. The one or more computer-readable media of claim 26, wherein the
system information block is System Information Block 1 (SIB1).

28. The one or more computer-readable media of claim 25, wherein: the
first TDD configuration is indicated by System Information Block 1 (SIB1)
of PCell; and the second TDD configuration is indicated by SIB1 of SCell.

29. The one or more computer-readable media of claim 25, wherein the
instructions, when executed, further cause the mobile device to: select
the reference TDD configuration whose uplink subframes are the same as
uplink subframes common between the first TDD configuration and the
second TDD configuration.

30. The one or more computer-readable media of claim 25, wherein the
instructions, when executed, cause the mobile device to: select the first
TDD configuration as the reference TDD configuration if all downlink
subframes of the second TDD configuration are a subset of all downlink
subframes of the first TDD configuration; and select the second TDD
configuration as the reference TDD configuration if all downlink
subframes of the second TDD configuration are a superset of all downlink
subframes of the first TDD configuration.

31. The one or more computer-readable media of claim 25, wherein the
instructions, when executed, cause the mobile device to: select TDD
downlink/uplink (DL/UL) configuration 4 as the reference TDD
configuration, if the first TDD configuration is TDD DL/UL configuration
1 and the second TDD configuration is TDD DL/UL configuration 3; select
TDD DL/UL configuration 5 as the reference TDD configuration, if the
first TDD configuration is TDD DL/UL configuration 2 and the second TDD
configuration is TDD DL/UL configuration 3; and select TDD DL/UL
configuration 5 as the reference TDD configuration, if the first TDD
configuration is TDD DL/UL configuration 2 and the second TDD
configuration is TDD DL/UL configuration 4.

32. The one or more computer-readable media of claim 25, wherein the
instructions, when executed, cause the mobile device to: select TDD
downlink/uplink (DL/UL) configuration 4 as the reference TDD
configuration, if the first TDD configuration is TDD DL/UL configuration
3 and the second TDD configuration is TDD DL/UL configuration 1; select
TDD DL/UL configuration 5 as the reference TDD configuration, if the
first TDD configuration is TDD DL/UL configuration 3 and the second TDD
configuration is TDD DL/UL configuration 2; and select TDD DL/UL
configuration 5 as the reference TDD configuration, if the first TDD
configuration is TDD DL/UL configuration 4 and the second TDD
configuration is TDD DL/UL configuration 2.

33. The one or more computer-readable media of claim 25, wherein
acknowledgement information includes HARQ-acknowledgement (HARQ-ACK)
signals, wherein only HARQ-ACK signals associated with the downlink data
of the SCell are transmitted according to the HARQ timing of the
reference TDD configuration, wherein HARQ-ACK signals associated with
downlink data of the PCell are transmitted only according to the HARQ
timing of the first TDD configuration.

34. The one or more computer-readable media of claim 25, wherein the
instructions, when executed, further cause the mobile device to: transmit
a positive or negative acknowledgement according to the HARQ timing of
the reference TDD configuration through at least one uplink subframe.

35. The one or more computer-readable media of claim 25, wherein each of
the first, second, and reference TDD configurations include at least one
of TDD downlink/uplink (DL/UL) configurations 0-6.

36. A method, comprising: communicating, by a mobile device, with a base
station via first and second component carriers having different
frequency bands and time division duplexing (TDD) configurations;
receiving one or more downlink transmissions via the second component
carrier; selecting a hybrid automatic repeat request (HARQ) timing
sequence based on the TDD configurations of the first and second
component carriers; and transmitting one or more positive acknowledgment
and/or negative acknowledgement (ACK/NACK) signals, associated with the
one or more downlink transmissions, according to the selected HARQ timing
sequence.

37. The method of claim 36, wherein selecting the HARQ timing sequence
includes: identifying, by the mobile device, each downlink subframe of
the first and second component carriers as either a first type of
downlink subframe or a second type of downlink subframe, wherein each
downlink subframe of one of the first and second component carriers is
the first type if a corresponding subframe of the other of the first and
second component carriers is also a downlink subframe, wherein each
downlink subframe of the one of the first and second component carriers
is the second type if a corresponding subframe of the other of the first
and second component carriers is an uplink subframe; and selectively
transmitting, by the mobile device, the one or more ACK/NACK signals
associated with each downlink subframe based on whether the downlink
subframe is identified as the first type of downlink subframe or the
second type of downlink subframe.

38. The method of claim 37, wherein selectively transmitting the one or
more ACK/NACK signals includes transmitting the one or more ACK/NACK
signals according to the TDD configuration of the first component carrier
for each downlink subframe identified as the first type of downlink
subframe.

39. The method of claim 37, wherein selectively transmitting the one or
more ACK/NACK signals includes transmitting the one or more ACK/NACK
signals according to the TDD configuration of the second component
carrier for each downlink subframe of the second component carrier
identified as the second type of downlink subframe and transmitting the
one or more ACK/NACK signals according to the TDD configuration of the
first component carrier for each downlink subframe of the first component
carrier identified as the second type of downlink subframe.

40. The method of claim 37, wherein selectively transmitting the one or
more ACK/NACK signals includes transmitting the one or more ACK/NACK
signals according to a reference TDD configuration for each downlink
subframe of the second component carrier identified as the second type
and transmitting the one or more ACK/NACK signals according to the TDD
configuration of the first component carrier for each downlink subframe
of the first component carrier identified as the second type.

41. The method of claim 40, wherein the reference TDD configuration is
selected to contain uplink subframes that are the same as subframes that
are common to TDD configurations of both the first and second component
carriers.

42. The method of claim 37, wherein each of the TDD configurations
include one of TDD downlink/uplink configurations 0-6.

43. An apparatus, comprising: a communication module configured to:
communicate with a base station via first and second component carriers
having different frequency bands and time division duplexing (TDD)
configurations, wherein a first one of the first and second component
carriers corresponds to a primary serving cell and a second one of the
first and second component carriers corresponds to a secondary serving
cell; and receive one or more downlink transmissions via the second
component carrier; and a hybrid automatic repeat request (HARQ) module
coupled with the communication module and configured to: select a HARQ
timing sequence based on the TDD configurations of the first and second
component carriers; and generate one or more positive acknowledgment
and/or negative acknowledgement (ACK/NACK) signals, associated with the
one or more downlink transmissions, wherein the communication module is
further configured to transmit the one or more ACK/NACK signals according
to the selected HARQ timing sequence.

44. The apparatus of claim 43, wherein the HARQ module is further
configured to: select the HARQ timing sequence that includes uplink
subframes that are the same as uplink subframes common between the TDD
configurations of the first and second component carriers.

45. The apparatus of claim 43, wherein the HARQ timing sequence is based
on a reference TDD configuration that is different from the TDD
configurations of the first and second component carriers.

46. The apparatus of claim 43, wherein the HARQ timing sequence is based
on a reference TDD configuration, and the HARQ module is configured to:
select the TDD configuration of the first component carrier as the
reference TDD configuration if all downlink subframes of the TDD
configuration of the second component carrier are a subset of all
downlink subframes of the TDD configuration of the first component
carrier.

47. The apparatus of claim 43, wherein the HARQ timing sequence is based
on a reference TDD configuration, and the HARQ module is configured to:
select the TDD configuration of the second component carrier as the
reference TDD configuration if all downlink subframes of the TDD
configuration of the second component carrier are a superset of all
downlink subframes of the TDD configuration of the first component
carrier.

48. The apparatus claim 43, wherein each of the TDD configurations
includes one of TDD downlink/uplink (DL/UL) configurations 0-6.

49. The apparatus of claim 43, wherein the apparatus comprises a mobile
phone, a netbook, a laptop, an electronic tablet, or a data system of a
vehicle.

51. One or more computer-readable media having instructions that, when
executed, cause a mobile device to: determine a primary serving cell
(PCell) is established with a first time-division duplexing (TDD)
configuration and a secondary serving (SCell) is established with a
second TDD configuration; select TDD downlink/uplink (DL/UL)
configuration 4 as a reference TDD configuration, if the first TDD
configuration is TDD DL/UL configuration 1 and the second TDD
configuration is TDD DL/UL configuration 3; select TDD DL/UL
configuration 5 as the reference TDD configuration, if the first TDD
configuration is TDD DL/UL configuration 2 and the second TDD
configuration is TDD DL/UL configuration 3 or TDD DL/UL configuration 4;
select TDD DL/UL configuration 4 as the reference TDD configuration, if
the first TDD configuration is TDD DL/UL configuration 3 and the second
TDD configuration is TDD DL/UL configuration 1; and select TDD DL/UL
configuration 5 as the reference TDD configuration, if the second TDD
configuration is TDD DL/UL configuration 2 and the first TDD
configuration is TDD DL/UL configuration 3 or TDD DL/UL configuration 4.

52. The one or more computer-readable media of claim 51, wherein the
instructions, when executed, further cause a mobile device to: transmit
acknowledgement information associated with the downlink data according
to a hybrid automatic repeat request (HARQ) timing of the reference TDD
configuration.

[0002] Embodiments of the present invention relate generally to the field
of communications, and more particularly, to selection of acknowledgement
timing in wireless communication networks.

BACKGROUND INFORMATION

[0003] A time division duplex (TDD) system, in wireless communications,
may offer flexibility in resource utilization. For example, a TDD system
may use different TDD configurations to match uplink and downlink traffic
characteristics of a wireless communications cell. The flexibility of
using different TDD configurations, may permit the ratio between
available uplink (UL) and downlink (DL) resources to range from 3UL:2DL
to 1UL:9DL.

[0004] Release 10, of 3rd Generation Partnership Project's (3GPP)
long term evolution-advanced (LTE-A) communications standard, may limit
support of the aggregation of TDD Component Carriers (CCs) to the same
uplink/downlink (UL/DL) TDD configurations. While such limitations may
have simplified the design and operation within the standard, such
limitation may have limited potential for greater data throughput.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Embodiments of the invention are illustrated by way of example, and
not by way of limitation, in the figures of the accompanying drawings in
which like reference numerals refer to similar elements.

[0006]FIG. 1 schematically illustrates a wireless communication network
in accordance with various embodiments.

[0009]FIG. 4 is a flowchart illustrating selection of an HARQ signal
scheduling configuration in accordance with various embodiments.

[0010]FIG. 5 schematically depicts an example of selecting a HARQ signal
scheduling configuration in accordance with various embodiments.

[0011]FIG. 6 schematically illustrates an example of HARQ signal
scheduling in accordance with various embodiments.

[0012] FIG. 7 is a flowchart illustrating selection of HARQ signal
scheduling for downlink subframes in accordance with various embodiments.

[0013]FIG. 8 schematically illustrates an example of an HARQ signal
scheduling diagram in accordance with various embodiments.

[0014]FIG. 9 schematically illustrates an example of an HARQ signal
scheduling diagram in accordance with various embodiments.

[0015]FIG. 10 schematically depicts an example system in accordance with
various embodiments.

DESCRIPTION OF THE EMBODIMENTS

[0016] Illustrative embodiments of the present disclosure include, but are
not limited to, methods, systems, and apparatuses for selection of
acknowledgement signal timing in a wireless communication network.

[0017] Various aspects of the illustrative embodiments will be described
using terms commonly employed by those skilled in the art to convey the
substance of their work to others skilled in the art. However, it will be
apparent to those skilled in the art that some alternate embodiments may
be practiced using with portions of the described aspects. For purposes
of explanation, specific numbers, materials, and configurations are set
forth in order to provide a thorough understanding of the illustrative
embodiments. However, it will be apparent to one skilled in the art that
alternate embodiments may be practiced without the specific details. In
other instances, well-known features are omitted or simplified in order
to not obscure the illustrative embodiments.

[0018] Further, various operations will be described as multiple discrete
operations, in turn, in a manner that is most helpful in understanding
the illustrative embodiments; however, the order of description should
not be construed as to imply that these operations are necessarily order
dependent. In particular, these operations need not be performed in the
order of presentation.

[0019] The phrase "in one embodiment" is used repeatedly. The phrase
generally does not refer to the same embodiment; however, it may. The
terms "comprising," "having," and "including" are synonymous, unless the
context dictates otherwise. The phrase "A/B" means "A or B". The phrase
"A and/or B" means "(A), (B), or (A and B)". The phrase "at least one of
A, B and C" means "(A), (B), (C), (A and B), (A and C), (B and C) or (A,
B and C)". The phrase "(A) B" means "(B) or (A B)", that is, A is
optional.

[0020] Although specific embodiments have been illustrated and described
herein, it will be appreciated by those of ordinary skill in the art that
a wide variety of alternate and/or equivalent implementations may be
substituted for the specific embodiments shown and described, without
departing from the scope of the embodiments of the present disclosure.
This application is intended to cover any adaptations or variations of
the embodiments discussed herein. Therefore, it is manifestly intended
that the embodiments of the present disclosure be limited only by the
claims and the equivalents thereof.

[0021] As used herein, the term "module" may refer to, be part of, or
include an Application Specific Integrated Circuit (ASIC), an electronic
circuit, a processor (shared, dedicated, or group) and/or memory (shared,
dedicated, or group) that execute one or more software or firmware
programs, a combinational logic circuit, and/or other suitable components
that provide the described functionality.

[0022]FIG. 1 schematically illustrates a wireless communication network
100 in accordance with various embodiments. Wireless communication
network 100 (hereinafter "network 100") may be an access network of a 3rd
Generation Partnership Project (3GPP) long-term evolution (LTE) network
such as evolved universal mobile telecommunication system (UMTS)
terrestrial radio access network (E-UTRAN). The network 100 may include a
base station, e.g., enhanced node base station (eNB) 104, configured to
wirelessly communicate with a mobile device or terminal, e.g., user
equipment (UE) 108. While embodiments of the present invention are
described with reference to an LTE network, some embodiments may be used
with other types of wireless access networks.

[0023] eNB 104 may include a receiver module 120 with which to receive
signals from UE 108 via one or more antennas 130. eNB 104 may include a
transmitter module 124 with which to transmit signals to UE 108 via one
or more antennas 130. eNB 104 may also include a processor module 128
coupled between receiver module 120 and transmitter module 124 and
configured to encode and decode information communicated by the signals.

[0024] In embodiments in which the UE 108 is capable of utilizing carrier
aggregation (CA), a number of component carriers (CCs) may be aggregated
for communication between the eNB 104 and the UE 108. In an initial
connection establishment, the UE 108 may connect with a primary serving
cell (Pcell) of the eNB 104 utilizing a primary CC. This connection may
be used for various functions such as security, mobility, configuration,
etc. Subsequently, the UE 108 may connect with one or more secondary
serving cells (Scells) of the eNB 104 utilizing one or more secondary
CCs. These connections may be used to provide additional radio resources.

[0025] Each CC may support a number of communication channels according to
a release of the 3GPP LTE-advanced communication standard. For example,
each CC may support a physical downlink shared channel (PDSCH) for
transmission of downlink data. As another example, each CC may support
physical uplink control channel (PUCCH) or/and physical uplink shared
channel (PUSCH) to carry information between UE 108 and eNB 104. A CC may
include a plurality of uplink and downlink subframes for carrying
information between eNB 104 and UE 108. A single 10 ms radio frame may
include ten subframes.

[0026] The CCs may be configured to transport information according to a
time domain duplexing (TDD) communication protocol. Each CC may be
scheduled to transport data to UE 108 or transport data to eNB 104
according to one of several TDD configurations. For example, with
reference to Table 1, each CC may be assigned to transport data

and/or control signals according to one of TDD configurations 0-6. A
primary CC and secondary CC may both be configured with the same TDD
configuration, or with different TDD configurations. In general, each of
subframes 0-9 that is labeled with a "D" or an "S" is a subframe with
which UE 108 receives data from eNB 104, and each of subframes 0-9 that
is labeled with a "U" is a subframe through which UE 108 transmits data
to eNB 104.

[0027] eNB 104 may be configured to communicate some information solely by
the PCell and be configured to communicate other information by either
the PCell or the SCell. For example, eNB 104 may be configured to receive
acknowledgment signals from UE 108 solely through the PCell. According
one embodiment, the acknowledgment signals may be hybrid adaptive repeat
and request (HARQ) signals corresponding to a positive acknowledgment
(ACK) of receipt of data and a negative acknowledgment (NACK) of receipt
of data. In embodiments, UE 108 may be configured to transmit ACK/NACK
signals to notify eNB 104 that transmitted data has or has not been
received.

[0028] UE 108 may be configured to determine a schedule with which to
transmit ACK/NACK signals to eNB 104. UE 108 may include a receiver
module 144, a transmitter module 148, a processor module 152, and one or
more suitable antennas 156. Receiver module 144 and transmitter module
148 may be coupled to one or more suitable antennas 156 to transmit and
receive wireless signals to/from eNB 104.

[0029] Processor module 152 may be coupled to receiver module 144 and
transmitter module 148 and be configured to decode and encode information
transmitted in signals communicated between the UE 108 and the eNB 104.
Processor module may include a communication module 154 and an HARQ
module 158. Processor module 152 may be configured to use communication
module 154 to transmit information in uplink subframes of the PCell,
e.g., on CC--0, according to the scheduling of a first TDD
configuration at a first frequency. Processor module 152 may also be
configured to transmit information in uplink subframes of the SCell,
e.g., on CC--1, according to a second TDD configuration at a second
frequency that is different from the first frequency. According to one
embodiment, the difference between transmission frequencies of CC--0
and CC--1 may range from hundreds of kilohertz to tens of Gigahertz,
in accordance with inter-band carrier aggregation.

[0030] As will be described in more detail hereafter, processor module 152
may be configured to selectively transmit ACK/NACK information for SCell
communications via a schedule of a TDD UL-DL configuration that is
different than the TDD configuration of SCell. In embodiments, processor
module 152 may use HARQ module 158 to select HARQ timing sequence or
timing schedule based on one of the TDD configurations. HARQ module 158
may also generate the ACK/NACK information for processor module 152. The
HARQ module may be coupled to the communication module 154 and may be
configured to use the communication module 154 to transmit the generated
ACK/NACK information via the selected HARQ timing sequence.

[0031] Various embodiments of the present disclosure may enable a eNB to
schedule uplink and downlink data transmission with different TDD
configurations on component carriers. These features may advantageously
enable a communication system to transmit data information with higher
peak data rates than previous communication systems. However, some
information transmitted with a PCell and an SCell having different TDD
configurations may result in HARQ ACK/NACK resources conflicts. For
example, because HARQ ACK/NACK signals for both SCell and PCell may be
transmitted between UE 108 and eNB 104 solely via uplink subframes of
PCell, uplink subframe schedules of PCell may result in scheduling
conflicts for ACK/NACK information for SCell.

[0032] While many embodiments described herein, are described in a carrier
aggregation context, it will be understood that other embodiments may be
applicable to an embodiment in which the UE 108 and eNB 104 utilize a
single serving cell, with a single component carrier, for communications.
In these embodiments, the UE 108 may be configured, e.g., by receipt of
system information block 1 (SIB1) broadcast by the eNB 104, to
communicate data with the eNB 104 according to a first TDD UL-DL
configuration. The UE 108 may be further configured to transmit ACK/NACK
information via a HARQ timing sequence of a second TDD UL-DL
configuration. These and other embodiments will be described in further
detail.

[0033]FIG. 2 illustrates a diagram of HARQ ACK/NACK signal scheduling
that may be performed by processor module 152, according to embodiments.
FIG. 2 shows PCell configured with TDD configuration 1 (shown in Table
1), and SCell configured with TDD configuration 3. Each of lines 200
represent a link between downlink or special subframe data and the uplink
subframe that is designated to carry corresponding ACK/NACK information
back to an eNB.

[0034] According to the solution of FIG. 2, PDSCH HARQ timing on all
secondary serving cells (e.g., SCells) may follow the TDD UL-DL
configuration of the PCell to allow increased reuse of Rel-10 TDD
intra-band carrier aggregation design. For example, HARQ ACK/NACK
information for SCell may be configured to follow the HARQ scheduling of
TDD configuration 1 because TDD configuration 1 is the TDD configuration
of PCell. However, such a configuration of SCell HARQ ACK/NACK
information may result in some ACK/NACK information not being fed back to
eNB.

[0035] As illustrated, subframes 7 and 8 of the SCell in one radio frame
could not be scheduled and utilized by UEs using carrier aggregation with
the shown TDD configuration because PCell does not have the corresponding
resources for HARQ ACK/NACK transmission. Thus, while a solution that
substantially reuses carrier aggregation design of release 10 may appear
advantageous, such a solution also includes several weaknesses.

[0036] FIG. 3 illustrates a diagram of HARQ ACK/NACK signal scheduling
that may be performed by processor module 152, according to embodiments.
FIG. 3 illustrates an issue with merely scheduling the ACK/NACK
information of SCell subframes 7 and 8 into PCell uplink subframe 3. As
shown, ACK/NACK information of SCell subframes 9 and 0 may need to be
transmitted during a downlink subframe of PCell subframe 4 rather than
during a PCell uplink subframe. Thus, the solution illustrated by FIG. 3
may leave some ACK/NACK information without an uplink resource for
transmission.

[0037]FIG. 4 is a flowchart illustrating a method 400 of selecting a HARQ
scheduling configuration that may overcome the potential downsides
illustrated in FIGS. 2 and 3, in accordance with various embodiments.

[0038] At block 404, UE 108 may establish a PCell with a first TDD
configuration. In some embodiments, the UE 108 may establish the PCell
with the first TDD configuration based on information received in an SIB1
broadcast from a base station, e.g., eNB 104.

[0039] At block 408, UE 108 may establish an SCell communication channel
with a second TDD configuration. In some embodiments, the UE 108 may
establish the SCell with the second TDD configuration based on
information received, from the eNB 104, in radio resource control (RRC)
signaling through the PCell.

[0040] At block 412, UE 108 may determine which uplink subframes are
common to both the first and second TDD configurations. These may be
referred to as the common UL subframes.

[0041] At block 416, UE 108 may select a reference TDD configuration
having uplink subframes that are the same as the common UL subframes. For
example, the uplink subframes of the selected HARQ TDD configuration may
be the same as the common uplink subframes, no more and no less.

[0042] UE 108 may determine the reference TDD configuration based on
information shown in Table 2. Table 2 (below) shows an x-axis and a
y-axis corresponding to TDD

TABLE-US-00002
TABLE 2
HARQ timing decision table
##STR00001##

configurations 0-6 of the PCell and Scell, respectively. For example, if
a PCell were configured with TDD configuration 4 and an SCell were
configured with TDD configuration 2, UE 108 may select TDD configuration
5 as the reference TDD configuration.

[0043] The cross-hatched portions of Table 2 are instances in which the
reference TDD configuration is neither the TDD configuration of the Pcell
or the Scell.

[0044] The non-cross-hatched portions of Table 2 indicate a reference TDD
configuration that is either the TDD configuration of the PCell or the
TDD configuration of the SCell. The non-cross-hatched portions of Table 2
may be described in terms of downlink subframes of the TDD configurations
for the PCell and SCell. In embodiments, the TDD configuration of the
PCell is selected to be the reference TDD configuration if the set of
downlink subframes indicated by the SCell TDD configuration (e.g., SIB1
configuration) is a subset of the downlink subframes indicated by the
PCell TDD configuration (e.g., SIB1 configuration). The TDD configuration
of the SCell is selected to be the reference TDD configuration if the set
of downlink subframes indicated by the SCell TDD configuration is a
superset of the downlink subframes indicated by the PCell TDD
configuration.

[0045] Returning to FIG. 4, at block 424, UE 108 may transmit ACK/NACK
information for the SCell according to the scheduling of the reference
TDD configuration, e.g., TDD configuration 5.

[0046]FIG. 5 schematically depicts an example of selecting a reference
TDD configuration in accordance with various embodiments. As described
above in connection with method 400 and Table 2, box 504 encloses the
uplink subframes (2 and 3) that are common between the TDD configuration
of the PCell and the TDD configuration of the SCell. Of the TDD
configurations of Table 1, TDD configuration 4 is the TDD configuration
that includes uplink subframes 2 and 3. Additionally, Table 2 indicates
that TDD configuration 4 may be used with a PCell TDD configuration 1 and
an SCell TDD configuration 3. Therefore, TDD configuration 4 may be
selected as the HARQ TDD configuration in this embodiment.

[0047]FIG. 6 schematically illustrates an example of HARQ signal
scheduling in accordance with various embodiments. In particular, FIG. 6
shows that HARQ ACK/NACK information related to SCell communications may
be transmitted via PCell while the SCell and PCell are configured with
different TDD configurations. As illustrated, SCell may be configured
with TDD configuration 3, PCell may be configured with TDD configuration
1, and HARQ ACK/NACK information related to the SCell may be sent via
PCell by using HARQ scheduling of TDD configuration 4.

[0048] FIG. 7 is a flowchart illustrating a method 700 of selecting a
reference TDD configuration in accordance with various embodiments. UE
108 may execute method 700 as an alternative to or in combination with
method 400, according to various embodiments.

[0049] At block 704, UE 108 may identify each downlink subframe of
component carriers of both the PCell and the SCell as a type 1 subframe
or a type 2 subframe. UE 108 may identify a downlink subframe as a type 1
subframe if a corresponding subframe in the other component carrier is
also a downlink subframe. For example, a downlink subframe of subframe 6
in the PCell component carrier may be type 1 if subframe 6 of the SCell
component carrier is also a downlink subframe. UE 108 may identify a
downlink subframe as a type 2 subframe if a corresponding subframe in the
other component carrier is an uplink subframe. For example, if subframe 3
of the SCell CC is a downlink subframe and subframe 3 of the PCell CC is
an uplink subframe, then subframe 3 of the SCell CC may be a type 2
downlink subframe. In other words, each downlink subframe may be type 1
if the subframe is allocated similarly as a corresponding subframe of the
other component carrier and may be type 2 if the subframe is allocated
differently than a corresponding subframe of the other component carrier.

[0050] At block 706, UE 108 may select a downlink subframe from the PCell
or the SCell.

[0051] At block 708, UE 108 may determine whether a downlink subframe is
type 1. If the downlink subframe is type 1, then method 700 goes to block
712.

[0052] At block 712, UE 108 transmits ACK/NACK signals for the selected
downlink subframe according to a timing schedule of the TDD configuration
of the PCell. Method 700 then returns to block 704 for the next downlink
subframe.

[0053] Returning to block 708, if the downlink subframe is not type 1,
then method 700 goes to either block 716 (option 1) or block 718 (option
2).

[0054] At block 716, UE 108 transmits ACK/NACK signals for the downlink
subframe according to a timing schedule of the TDD configuration of the
serving cell in which the downlink subframe resides. For example, if the
downlink subframe is type 2 in the PCell, then UE 108 transmits ACK/NACK
signals for the downlink subframe according to the timing schedule of the
TDD configuration of the PCell. If the downlink subframe is type 2 in the
SCell, then UE 108 transmits ACK/NACK signals for the downlink subframe
according to the timing schedule of the TDD configuration of the SCell.
Method 700 then returns to block 704 for the next downlink subframe.

[0055] Returning to block 708, if the downlink subframe is not type 1,
then method 700 may optionally go to block 718 instead of block 716.

[0056] At block 718, UE 108 may determine if the type 2 downlink subframe
resides in the PCell. If the selected downlink subframe resides in the
PCell, method 700 may go to block 712. If the selected downlink subframe
resides in the SCell, method 700 may go to block 720.

[0057] At block 720, UE 108 may transmit ACK/NACK signals for selected
subframe according to the HARQ-ACK timing schedule of a reference TDD
configuration determined by method 400. Method 700 may then return to
block 704.

[0058]FIG. 8 schematically illustrates an example of an HARQ signal
scheduling diagram in accordance with various embodiments. For example,
as discussed above in connection with method 700, downlink subframes (and
special subframes) of the PCell and SCell may be identified as type 1, if
the corresponding of the other serving cell are also downlink subframes.
Box 804 and box 808 show that subframes 0, 1, 5, and 6 of both the PCell
and SCell may be identified as type 1. Accordingly, the HARQ ACK/NACK
information of the type 1 subframes may be transmitted according to the
TDD configuration of the PCell, e.g., TDD configuration 0.

[0059] Downlink subframes of the PCell and the SCell may be identified as
type 2, if the corresponding subframes of the other serving cell are
uplink subframes. Subframes 3, 4, 8, and 9 of SCell include hash marks to
indicate that they may be type 2 subframes. In accordance with method
700, the HARQ ACK/NACK information of the type 2 subframes of the SCell
may be transmitted according to the HARQ timing of the TDD configuration
of the SCell, e.g., TDD configuration 2. It may be noted that TDD
configuration 2 would be selected either in option 1 or 2 of method 700
in this instance.

[0060]FIG. 9 schematically illustrates an example of a HARQ signal
scheduling diagram in accordance with various embodiments. According to
one embodiment, downlink subframes may be identified as type 1 or type 2.
In this embodiment, subframes 0, 1, 5, 6, and 9 of the PCell and the
SCell may be type 1 subframes, while subframe 4 of the PCell and
subframes 7 and 8 of the SCell may be type 2 subframes. As described in
method 700, the HARQ timing of the TDD configuration of the PCell will be
used for the type 1 subframes, whether they are in the PCell or the
SCell.

[0061] With respect to the type 2 subframe of the PCell, i.e., subframe 4,
the HARQ ACK/NACK information may be scheduled according to the TDD
configuration of the PCell, e.g., TDD configuration 1. This may be the
case with either option 1 or 2 of method 700.

[0062] With respect to the type 2 subframes of the SCell, i.e., subframes
7 and 8, the HARQ ACK/NACK information may be feedback according to the
HARQ timing of TDD configuration 3, e.g., TDD configuration of the SCell,
in the event option 1 of method 700 were used. However, if option 2 of
method 700 were used, the HARQ ACK/NACK information may be scheduled
according to a HARQ TDD configuration selected according to method 400.
In this instance, the HARQ TDD configuration may be TDD configuration 4,
given that the PCell has a TDD configuration 1 and SCell has a TDD
configuration 3.

[0063] The eNB 104 and UE 108 described herein may be implemented into a
system using any suitable hardware and/or software to configure as
desired. FIG. 10 illustrates, for one embodiment, an example system 1000
comprising one or more processor(s) 1004, system control logic 1008
coupled with at least one of the processor(s) 1004, system memory 1012
coupled with system control logic 1008, non-volatile memory (NVM)/storage
1016 coupled with system control logic 1008, and a network interface 1020
coupled with system control logic 1008.

[0064] Processor(s) 1004 may include one or more single-core or multi-core
processors. Processor(s) 1004 may include any combination of
general-purpose processors and dedicated processors (e.g., graphics
processors, application processors, baseband processors, etc.). In an
embodiment in which the system 1000 implements UE 108, processors(s) 1004
may include processor module 152 and be configured to execute the
embodiments of FIGS. 2-9 in accordance with various embodiments. In an
embodiment in which the system 1000 implements eNB 104, processor(s) 1004
may include processor module 128 and be configured to decode the HARQ
ACK/NACK information transmitted by UE 108.

[0065] System control logic 1008 for one embodiment may include any
suitable interface controllers to provide for any suitable interface to
at least one of the processor(s) 1004 and/or to any suitable device or
component in communication with system control logic 1008.

[0066] System control logic 1008 for one embodiment may include one or
more memory controller(s) to provide an interface to system memory 1012.
System memory 1012 may be used to load and store data and/or
instructions, for example, for system 1000. System memory 1012 for one
embodiment may include any suitable volatile memory, such as suitable
dynamic random access memory (DRAM), for example.

[0067] NVM/storage 1016 may include one or more tangible, non-transitory
computer-readable media used to store data and/or instructions, for
example. NVM/storage 1016 may include any suitable non-volatile memory,
such as flash memory, for example, and/or may include any suitable
non-volatile storage device(s), such as one or more hard disk drive(s)
(HDD(s)), one or more compact disk (CD) drive(s), and/or one or more
digital versatile disk (DVD) drive(s), for example.

[0068] The NVM/storage 1016 may include a storage resource physically part
of a device on which the system 1000 is installed or it may be accessible
by, but not necessarily a part of, the device. For example, the
NVM/storage 1016 may be accessed over a network via the network interface
1020.

[0069] System memory 1012 and NVM/storage 1016 may respectively include,
in particular, temporal and persistent copies of instructions 1024.
Instructions 1024 may include instructions that when executed by at least
one of the processor(s) 1004 result in the system 1000 implementing a one
or both of methods 400 and 700 as described herein. In some embodiments,
instructions 1024, or hardware, firmware, and/or software components
thereof, may additionally/alternatively be located in the system control
logic 1008, the network interface 1020, and/or the processor(s) 1004.

[0070] Network interface 1020 may have a transceiver 1022 to provide a
radio interface for system 1000 to communicate over one or more
network(s) and/or with any other suitable device. The transceiver 1022
may be implement receiver module 144 and/or transmitter module 148. In
various embodiments, the transceiver 1022 may be integrated with other
components of system 1000. For example, the transceiver 1022 may include
a processor of the processor(s) 1004, memory of the system memory 1012,
and NVM/Storage of NVM/Storage 1016. Network interface 1020 may include
any suitable hardware and/or firmware. Network interface 1020 may include
a plurality of antennas to provide a multiple input, multiple output
radio interface. Network interface 1020 for one embodiment may include,
for example, a network adapter, a wireless network adapter, a telephone
modem, and/or a wireless modem.

[0071] For one embodiment, at least one of the processor(s) 1004 may be
packaged together with logic for one or more controller(s) of system
control logic 1008. For one embodiment, at least one of the processor(s)
1004 may be packaged together with logic for one or more controllers of
system control logic 1008 to form a System in Package (SiP). For one
embodiment, at least one of the processor(s) 1004 may be integrated on
the same die with logic for one or more controller(s) of system control
logic 1008. For one embodiment, at least one of the processor(s) 1004 may
be integrated on the same die with logic for one or more controller(s) of
system control logic 1008 to form a System on Chip (SoC).

[0072] The system 1000 may further include input/output (I/O) devices
1032. The I/O devices 1032 may include user interfaces designed to enable
user interaction with the system 1000, peripheral component interfaces
designed to enable peripheral component interaction with the system 1000,
and/or sensors designed to determine environmental conditions and/or
location information related to the system 1000.

[0073] In various embodiments, the user interfaces could include, but are
not limited to, a display (e.g., a liquid crystal display, a touch screen
display, etc.), a speaker, a microphone, one or more cameras (e.g., a
still camera and/or a video camera), a flashlight (e.g., a light emitting
diode flash), and a keyboard.

[0074] In various embodiments, the peripheral component interfaces may
include, but are not limited to, a non-volatile memory port, an audio
jack, and a power supply interface.

[0075] In various embodiments, the sensors may include, but are not
limited to, a gyro sensor, an accelerometer, a proximity sensor, an
ambient light sensor, and a positioning unit. The positioning unit may
also be part of, or interact with, the network interface 1020 to
communicate with components of a positioning network, e.g., a global
positioning system (GPS) satellite.

[0076] In various embodiments, the system 1000 may be a mobile computing
device such as, but not limited to, a laptop computing device, a tablet
computing device, a netbook, a mobile phone, etc. In various embodiments,
system 1000 may have more or less components, and/or different
architectures.

[0077] The disclosure may include various example embodiments disclosed
below.

[0078] According to various example embodiments, a method may include
establishing, by a mobile device, a primary serving cell (PCell) and a
secondary serving (SCell) with a base station. The PCell may be
established with a first TDD configuration, and the SCell may be
established with a second TDD configuration. The method my include
receiving, by the mobile device, downlink data through the SCell, and
selecting, by the mobile device, a reference TDD configuration based on
the first and second TDD configurations. The method may include
transmitting acknowledgement information associated with the downlink
data according to a hybrid automatic repeat request (HARD) timing of the
reference TDD configuration.

[0079] In embodiments, the reference TDD configuration may be different
from the TDD configuration indicated by a system information block of the
SCell.

[0080] In embodiments, the system information block may be System
Information Block 1 (SIB1).

[0081] In embodiments, the first TDD configuration may be indicated by SIB
1 of PCell, and

[0082] the second TDD configuration may be indicated by SIB1 of SCell.

[0083] In embodiments, the method may further include determining uplink
subframes common between the first TDD configuration and the second TDD
configuration, and selecting the reference TDD configuration based on the
determined uplink subframes common between the first TDD configuration
and the second TDD configuration.

[0084] In embodiments, selecting the reference TDD configuration may
include identifying the uplink subframes common between the first TDD
configuration and the second TDD configuration, and may include selecting
the reference TDD configuration based on a determination that uplink
subframes of the reference TDD configuration may be the same as the
common uplink subframes between the first TDD configuration and the
second configuration.

[0085] In embodiments, selecting the reference TDD configuration may
include selecting the first TDD configuration as the reference TDD
configuration if all downlink subframes of the second TDD configuration
are a subset of all downlink subframes of the first TDD configuration,
and may include selecting the second TDD configuration as the reference
TDD configuration if all downlink subframes of the second TDD
configuration are a superset of all downlink subframes of the first TDD
configuration.

[0086] In embodiments, selecting the reference TDD configuration may
include selecting TDD DL/UL configuration 4, if the first TDD
configuration is TDD DL/UL configuration 1 and the second TDD
configuration is TDD DL/UL configuration 3; selecting TDD DL/UL
configuration 5, if the first TDD configuration is TDD DL/UL
configuration 2 and the second TDD configuration is TDD DL/UL
configuration 3; and selecting TDD DL/UL configuration 5, if the first
TDD configuration is TDD DL/UL configuration 2 and the second TDD
configuration is TDD DL/UL configuration 4.

[0087] In embodiments, selecting the acknowledgment TDD may include
selecting TDD DL/UL configuration 4, if the first TDD configuration is
TDD DL/UL configuration 3 and the second TDD configuration is TDD DL/UL
configuration 1; selecting TDD DL/UL configuration 5, if the first TDD
configuration is TDD DL/UL configuration 3 and the second TDD
configuration is TDD DL/UL configuration 2; and selecting TDD DL/UL
configuration 5, if the first TDD configuration is TDD DL/UL
configuration 4 and the second TDD configuration is TDD DL/UL
configuration 2.

[0088] In embodiments, acknowledgement information may include hybrid
automatic repeat request acknowledgement (HARQ-ACK) signals, and only
HARQ-ACK signals associated with the downlink data of the SCell may be
transmitted according to the HARQ timing of the reference TDD
configuration. HARQ-ACK signals associated with downlink data of the
PCell may be transmitted only according to the HARQ timing of the first
TDD configuration.

[0089] In embodiments, transmitting the acknowledgement information may
include transmitting a positive or negative acknowledgement according to
the HARQ timing of the reference TDD configuration through at least one
uplink subframe.

[0090] In embodiments, each of the first, second, and reference TDD
configurations may include at least one of TDD downlink/uplink (DL/UL)
configurations 0-6 associated with release 8 of 3rd Generation
Partnership Project's long term evolution (LTE) advanced wireless
communication standard.

[0091] According to various example embodiments, a method may include
communicating, by a mobile device, with a base station via first and
second component carriers having different frequency bands and time
division duplexing (TDD) configurations. The method may include receiving
one or more downlink transmissions via the second component carrier, and
selecting a hybrid automatic repeat request (HARQ) timing sequence based
on the TDD configurations of the first and second component carriers. The
method may include transmitting one or more positive acknowledgment
and/or negative acknowledgement (ACK/NACK) signals, associated with the
one or more downlink transmissions, according to the selected HARQ timing
sequence.

[0092] In embodiments, selecting the HARQ timing sequence may include
identifying, by the mobile device, each downlink subframe of the first
and second component carriers as either a first type of downlink subframe
or a second type of downlink subframe. Each downlink subframe of one of
the first and second component carriers may be the first type if a
corresponding subframe of the other of the first and second component
carriers is also a downlink subframe. Each downlink subframe of the one
of the first and second component carriers may be the second type if a
corresponding subframe of the other of the first and second component
carriers is an uplink subframe. Selecting the HARQ timing sequence may
also include selectively transmitting, by the mobile device, the one or
more ACK/NACK signals associated with each downlink subframe based on
whether the downlink subframe is identified as the first type of downlink
subframe or the second type of downlink subframe.

[0093] In embodiments, selectively transmitting the one or more ACK/NACK
signals may include transmitting the one or more ACK/NACK signals
according to the TDD configuration of the first component carrier for
each downlink subframe identified as the first type of downlink subframe.

[0094] In embodiments, selectively transmitting the one or more ACK/NACK
signals may include transmitting the one or more ACK/NACK signals
according to the TDD configuration of the second component carrier for
each downlink subframe of the second component carrier identified as the
second type of downlink subframe and transmitting the one or more
ACK/NACK signals according to the TDD configuration of the first
component carrier for each downlink subframe of the first component
carrier identified as the second type of downlink subframe.

[0095] In embodiments, selectively transmitting the one or more ACK/NACK
signals may include transmitting the one or more ACK/NACK signals
according to a reference TDD configuration for each downlink subframe of
the second component carrier identified as the second type and
transmitting the one or more ACK/NACK signals according to the TDD
configuration of the first component carrier for each downlink subframe
of the first component carrier identified as the second type.

[0096] In embodiments, the reference TDD configuration may be selected to
contain uplink subframes that are the same as subframes that are common
to TDD configurations of both the first and second component carriers.

[0097] In embodiments, each of the TDD configurations may include one of
configurations 0-6 associated with release 8 of 3rd Generation
Partnership Project's (3GPP) long term evolution (LTE) advanced wireless
communication standard.

[0098] In embodiments, the mobile device may be a mobile phone, a netbook,
a laptop, an electronic tablet, or a data system of a vehicle.

[0099] According to various example embodiments, at least one machine
readable medium may include a number of instructions that, in response to
being executed on a computing device, cause the computing device to carry
out any of the example embodiments of disclosed methods.

[0100] According to various example embodiments, an apparatus may include
a communication module configured to communicate with a base station via
first and second component carriers having different frequency bands and
time division duplexing (TDD) configurations. The communication module
may be configured to receive one or more downlink transmissions via the
second component carrier. The apparatus may include a hybrid automatic
repeat request (HARQ) module coupled with the communication module and
configured to select a HARQ timing sequence based on the TDD
configurations of the first and second component carriers. The HARQ
module may be configured to generate one or more positive acknowledgment
and/or negative acknowledgement (ACK/NACK) signals, associated with the
one or more downlink transmissions. The communication module may be
further configured to transmit the one or more ACK/NACK signals according
to the selected HARQ timing sequence.

[0101] In embodiments, the HARQ module may be further configured to
identify uplink subframes common between the TDD configurations of the
first and second component carriers. The selected HARQ timing sequence
may be a HARQ timing sequence of a reference TDD configuration having the
same uplink subframes as the identified common uplink subframes.

[0102] In embodiments, Each of the TDD configurations may include one of
TDD configurations 0-6 associated with release 8 of 3rd Generation
Partnership Project's long term evolution (LTE) advanced wireless
communication standard.

[0103] Although certain embodiments have been illustrated and described
herein for purposes of description, a wide variety of alternate and/or
equivalent embodiments or implementations calculated to achieve the same
purposes may be substituted for the embodiments shown and described
without departing from the scope of the present disclosure. This
application is intended to cover any adaptations or variations of the
embodiments discussed herein. Therefore, it is manifestly intended that
embodiments described herein be limited only by the claims and the
equivalents thereof.